Deep Time — a stratigraphy game

◀ Deep Time Games

Four games, a reference chart and the Cenozoic climate record, all keyed to the real geologic time scale: sequence the ages oldest-to-youngest, drill a core down through deep time, match minerals and dig-site finds, or survive the Hadean magma ocean. Pick a tab below — your progress saves on this device.

Three ways to drill the record: sequence events oldest-to-youngest, match each one to its period, or flip flashcards. Pick a deck to study one theme, or take the whole record mixed.

Which is oldest? Click it first.

Sink a borehole through deep time. Every strike drills you further into the past — cross a boundary and the core yields a discovery. Bank research points, upgrade the rig, and reach the Hadean crust at 4,600 Ma.

Surface

0.00 Ma deep

Present day — hand on the drill.

Research points: 0

rig idle

surface0%4600 Ma

The rig

Spend research points on a sharper bit or steadier automation.

Drill bit — power per strike

Automation — passive descent

Core log

What the borehole has passed through, most recent first.

Nothing logged yet. Start drilling.

Swap two neighbours to line up three or more of a kind and clear them. Match four and you forge a tool — the archaeologist's trowel or the geologist's rock hammer, which clears a whole row or column. Five makes a bigger charge. Same board, two skins — flip between the geology and anthropology themes any time.

In a smelter, the slag floats on the molten iron. The newborn Earth ran the same separation at planetary scale — iron sank to forge the core, and the light silicate slag rose, chilled, and stiffened into the first crust. You live on that slag. Hop raft to raft across the Hadean magma ocean, pocket zircons, dodge the bombardment, and hold on from 4,500 Ma to the dawn of the Archean.

Click or tap a raft inside the dashed ring to hop to it — arrow keys and WASD work too. New slag freezes at the glowing ridge on the left; the trench on the right eats everything that drifts into it. Don't ride your raft all the way down.

The whole record at a glance — the International Chronostratigraphic Chart, read the way strata stack: youngest at the top, the Hadean crust at the bottom. The colours are the chart's own; every card in both games is keyed to them.

Ages in millions of years before present (Ma), after the ICS 2023 time scale. Boundary dates are rounded; several carry real uncertainty of a million years or more.

Sixty-six million years of climate, read from the shells of bottom-dwelling foraminifera in deep-sea cores. This is the record that gives every warming and cooling event its name — and it is the single most-cited curve in Cenozoic geology.

benthic δ¹⁸O — smoothed named events — click one Curve is schematic, shaped on the CENOGRID compilation (Westerhold et al., Science 2020)

What δ¹⁸O actually measures

Two signals in one number

The ratio of ¹⁸O to ¹⁶O in a foram shell depends on both the temperature of the water it grew in and the isotopic composition of the ocean itself. Colder water leaves more ¹⁸O in the shell; and when ice sheets grow, they preferentially lock up the lighter ¹⁶O, enriching the whole ocean in ¹⁸O. Both push δ¹⁸O the same direction, which is exactly the problem: a rise means colder, or more ice, or both, and separating them takes independent evidence.

Why benthic, and why the axis is upside down

Surface-dwelling forams record local seasonal noise. Benthic forams live in deep water that is sourced from high latitudes and mixed globally, so they average out the noise and give something close to a global signal. The axis is conventionally plotted inverted — values increasing downward — so that up on the page means warmer, which is what everyone actually wants to read.

The overall shape

One long cooling, from a peak in the early Eocene to today, interrupted by optima and punctuated by two step changes: Antarctic glaciation at 34 Ma and Northern Hemisphere glaciation at about 2.7 Ma. Steps, not a smooth ramp — the system sits in a state, then reorganises. Long-term declining atmospheric CO₂ is the usual explanation for the trend, with tectonics setting the boundary conditions: opening ocean gateways, closing the Isthmus of Panama, raising the Himalaya.

Reading the δ¹³C alongside it

The companion carbon curve tracks where carbon is stored. A sharp negative excursion means a large mass of isotopically light carbon — organic or methane-derived — entered the ocean and atmosphere quickly. That is the fingerprint at the PETM, and it is why the PETM is studied so hard: it is the closest natural analogue we have to injecting carbon fast.

Why a sedimentologist cares

Every one of these events has a sedimentary signature, and the curve is the frame you hang them on.

Weathering intensity tracks climate

Warm, wet intervals drive hydrolysis harder, so mudstones deposited during them carry higher CIA values and more kaolinite. The Chemical Index of Alteration in an ancient shale is a palaeoclimate proxy precisely because this curve is real — provided you have corrected for K-metasomatism first.

Ice volume drives sequence stratigraphy

Before 34 Ma there was little continental ice and sea-level cycles were modest. After it, and especially after 2.7 Ma, glacio-eustasy dominates: high-amplitude, high-frequency sea-level swings that generate the stacked parasequences and unconformity-bounded sequences you correlate. The character of the stratigraphic record changes because the climate state did.

The carbonate compensation depth moves

The CCD deepened sharply at the Eocene–Oligocene transition, so deep-sea sections that had been dissolving carbonate began preserving it. A change from clay to carbonate ooze in a core can be a chemical event rather than a change in productivity or depth — which is a good general warning about reading lithology straight as environment.